1. Field of the Invention
This invention relates to magnetic recording mediums such as, for example, magnetic disks, magnetic tapes and the like.
2. Description of the Prior Art
In recent years, magnetic heads have been remarkably improved particularly with respect to the type of material therefor, coupled with an improvement in mechanical arrangement of the head that a degree of floating of the magnetic head becomes smaller than as having been experienced heretofore. These improvements enable one to record information in magnetic recording mediums having high coercivity. Accordingly, there is a demand for high density information recording using magnetic recording mediums with high coercivity.
In the sixth Convention of the Applied Magnetic Society on November, 1982 and also in the seventh Convention of the Applied Magnetic Society on November, 1983, binary and ternary alloys where Pt is added to Co alloys for use in magnetic recording mediums have been reported from Nippon Electric Co., Ltd.
Moreover, those mediums having a CoNiPt magnetic layer formed on a Cr layer have been stated in Japanese Laid-open Patent Application Nos. 62-141628 and 61-142524.
For high density information recording, the magnetic layer should be imparted with high coercivity. The maximum coercivity attained by the known magnetic recording mediums is usually in the range of from about 1000 to 1200 Oe. For instance, the medium described in the Japanese Laid-open Patent Application No. 62-141628 has a coercivity of about 1200 Oe and that of the Japanese Laid-open Patent Application No. 61-142524 has a coercivity of about 1000 Oe.
The magnetic recording mediums obtained by addition of Pt to Co alloys as described above cannot be imparted with sufficiently high coercivity unless Pt is added at least in amounts of approximately 15 atomic percent. In view of the expensiveness of Pt, the mediums are not considered as practical.